The state of communications technology, particularly that which affects the Internet, is currently in flux and subject to rapid and often uncoordinated growth. The ubiquity and diversity of personal computers and set-top boxes has placed significant pressure on the providers of communications system infrastructure to accommodate the alarming increase in the number of new users that demand immediate access to Internet and other network resources. The rapid development of new and sophisticated software made available to users of such services places additional demands on system infrastructure.
The communications industry is expending considerable attention and investment on one particular technology, referred to as asynchronous transfer mode (ATM), as a possible solution to current and anticipated infrastructure limitations. Those skilled in the art understand ATM to constitute a communications networking concept that, in theory, addresses many of the aforementioned concerns, such as by providing a capability to manage increases in network load, supporting both real-time and non-real-time applications, and offering, in certain circumstances, a guaranteed level of service quality.
A conventional ATM service architecture typically provides a number of predefined quality of service classes, often referred to as service categories. Each of the service categories includes a number of quality of service (QoS) parameters which define the nature of the respective service category. In other words, a specified service category provides performance to an ATM virtual connection (VCC or VPC) in a manner specified by a subset of the ATM performance parameters. The service categories defined in the ATM Forum specification reference hereinbelow include, for example, a constant bit rate (CBR) category, a real-time variable bit rate (rt-VER) category, a non-real-time variable bit rate (nrt-VBR) category, an unspecified bit rate (UBR) category, and an available bit rate (ABR) category.
The constant bit rate service class is intended to support real-time applications that require a fixed quantity of bandwidth during the existence of the connection. A particular quality of service is negotiated to provide the CBR service, where the QoS parameters include characterization of the peak cell rate (PCR), the cell loss rate (CLR), the cell transfer delay (CTD), and the cell delay variation (CDV). Conventional ATM traffic management schemes guarantee that the user-contracted QoS is maintained in order to support, for example, real-time applications, such as circuit emulation and voice/video applications, which require tightly constrained delay variations.
The non-real-time VBR service class is intended to support non-real-time applications, where the resulting network traffic can be characterized as having frequent data bursts. Similarly, the real-time variable bit rate service category may be used to support "bursty" network traffic conditions. The rt-VBR service category differs from the nrt-VBR service category in that the former is intended to support real-time applications, such as voice and video applications. Both the real-time and non-real-time VBR service categories are characterized in terms of a peak cell rate (PCR), a sustainable cell rate (SCR), and a maximum burst size (MBS).
The unspecified bit rate (UBR) service category is often regarded as a "best effort service," in that it does not specify traffic-related service guarantees. As such, the UBR service category is intended to support non-real-time applications, including traditional computer communications applications such as file transfers and e-mail.
The available bit rate (ABR) service category provides for the allocation of available bandwidth to users by controlling the rate of traffic through use of a feedback mechanism. The feedback mechanism permits cell transmission rates to be varied in an effort to control or avoid traffic congestion, and to more effectively utilize available bandwidth. A resource management (RM) cell precedes the transmission of data cells, which is transmitted from source to destination and back to the source, in order to provide traffic information to the source.
Although the current ATM service architecture described above would appear to provide, at least at a conceptual level, viable solutions to the many problems facing the communications industry, ATM, as currently defined, requires implementation of a complex traffic management scheme in order meet the objectives articulated in the various ATM specifications and recommendations currently being considered. In order to effectively manage traffic flow in a network, conventional ATM traffic management schemes must assess a prodigious number of traffic condition indicators, including service class parameters, traffic parameters, quality of service parameters and the like. A non-exhaustive listing of such parameters and other ATM traffic management considerations is provided in ITU-T Recommendation I.371, entitled Traffic Control and Congestion Control in B-ISDN, and in Traffic Management Specification, version 4.0 (af-tm-0056.000, April 1996), published by the Technical Committee of the ATM Forum.
Some commentators have suggested that a solution to these problems may be found by increasing the bandwidth or capacity of the network (e.g., the Internet). Implementing this overly simplistic solution would require an appreciable investment of hardware, software, and, most likely, replacing existing communication lines with high bandwidth transmission lines, such as fiber optic lines. This suggested solution, however, would likely result in undisciplined network expansion and uncoordinated management of network traffic. Also, such a solution, if implemented, would appear to obviate the need for much of the sophisticated traffic management features currently defined in ATM specifications.
Another possible solution involves the implementation of cheaper, faster, and higher capacity network nodes. Although the cost of electronic components continues to generally decline, the complexity of current and proposed ATM service specifications continues to increase. In order to satisfy the traffic management requirements of the above-described ATM services, for example, sophisticated software and hardware is typically integrated into a network node. This increase in the complexity of node design and manufacture results in a corresponding increase in the cost of such network nodes.
Accordingly, there is a need in the communications industry for a network management architecture and method that is simple in concept and in its implementation, yet adequately addresses the quality of service requirements to support a range of network services, including real-time and non-real-time services. There exists a further need for a system and methodology that provides for the implementation of low cost, high throughput network nodes that accommodate both real-time and non-real-time connections. The present invention fulfills these and other needs which remain unaddressed by prior art network traffic management approaches.